This invention relates to the field of marine transport and more specifically to barge cargo transport. In particular, the present invention relates to connected or articulated tug and barge units, also known as articulated pusher boat and barge units used in the transport of petroleum products and other commodities.
Referring to FIGS. 1 and 2, the operation of the prior art arrangements between articulated tug and barge vessels will be described. In FIG. 1, tugboat 14 is shown approaching the stern of barge 10. In the stern of barge 10 is notch or well 12 which is sized to receive the bow of tugboat 14. Tugboat or pusher boat 14 approaches the stern of barge 10 and positions itself within notch 12 such that coupling unit 16, 16' of tugboat 14 aligns with vertical channels 18, 18' on barge 10. Once tugboat or pusher boat 14 is properly seated within notch or well 12 of barge 10, alignment is achieved between coupling unit 16, 16' and vertical channels 18, 18' at which time coupling unit 16, 16' is extended by the pusher boat operator to engage with teeth 28 of vertical channel 18 and teeth 28' (not shown) of vertical channel 18'. The advantages of this interconnection between the pusher boat or tugboat 14 and barge 10 are that the boat and barge are securely connected, and boat 14 has far greater control over the acceleration and deceleration of barge 10 and greater control over the direction of travel than would be available to the tug if tow lines were being used to pull the barge through the water.
One means for making the connection between boat 14 and barge 10 is through the use of a coupling unit as shown in FIG. 3. Coupling unit 16 of FIG. 3 operates to secure boat 14 to barge 10 through use of screw drive 36 which extends coupling unit helmet 30 outwardly from the side of boat 14 to connect with teeth 28 of vertical channels 18, 18' (FIG. 1). The operation of the particular coupling unit shown in FIG. 3 is fully discussed in U.S. Pat. No. 4,688,507 to Kuhlman, et al., and that patent specification is incorporated herein by reference.
Still referring to FIG. 3, the general operation of coupling unit 16 will be discussed. Once the pilot has navigated boat 14 into notch or well 12 of barge 10, cast component or helmet 30 of coupling unit 16 is extended toward vertical channels 18, 18' (FIG. 1). The extension of helmet 30 is initiated by operation of screw 36 which has steel ball 32 attached to one end and on which helmet 30 can pivot. The extension and retraction of screw 36 is operated by use of either low speed electric motor 46 or high speed electric motor 44. In the case of high speed electric motor 44, the force from motor 44 is communicated by shaft 42 to gear 38, the rotation of which causes rotation of screw 36. Rotation of screw 36, depending on the direction selected, will either extend or retract steel ball 32 and helmet 30 which are attached to screw 36. Referring now to FIGS. 4 and 5, the configuration of helmet or cast component 30 is shown. Helmet 30 is designed such that teeth 48 of helmet 30 engage teeth 28 of vertical channels 18, 18' of barge 10 (FIG. 1). It will be appreciated that upon extension of screw 36 of coupling unit 16 (FIG. 3) to bring helmet 30 in contact with vertical channels 18, 18' that teeth 48 of helmet 30 will engage with four of teeth 28 on the fore and aft sides of vertical channels 18, 18'. This design provides six faces of contact between helmet 30 and vertical channels 18, 18' thereby providing a very secure interconnection with a minimum of vertical play between the vertical channels 18, 18' and coupling units 16, 16'.
The manner of coupling tug and barge units just described provides a secure, dependable interconnection between a tug or pusher boat 14 and barge 10 and offers far greater control and maneuverability over barge 10 than the previously used methods of attaching tow cables to barges and pulling them through the water. It will be appreciated by examination of FIGS. 1 and 2 that the connection procedure between 11 boat 14 and barge 10 of directing boat 14 into notch 12 and positioning boat 14 such that coupling unit 16, 16' can be extended to fit into channels 18, 18', virtually requires that this coupling and uncoupling to be conducted in reasonably calm water. Any substantial movement between boat 14 and notch barge would prevent proper alignment of the boat and barge thereby defeating connection of coupling unit 16, 16' to vertical channels 18, 18'. In addition, attempting to engage or disengage boat 14 and barge 10 in rough waters can lead to uncontrolled contact between boat 14 and barge 10 resulting in damage to both vessels. Therefore, it is necessary that the connection between boat 14 and barge 10 be made in calm waters. Once the connection is achieved and the arrangement of FIG. 2 is presented, the boat and barge unit can tolerate very rough seas. One report on the device shown in U.S. Pat. No. 4,688,507 indicated that a boat and barge unit coupled by such a device withstood and traveled through a storm having waves in excess of 35 feet.
While this report to indicates the strength and durability of this type of extended screw ram and channel connection between the boat and barge combination, it will also be appreciated that uncoupling and re-coupling the boat 14 and barge 10 in rough seas is dangerous and very unlikely to be successful. The lack of success in coupling the boat and barge combination during rough seas is a result of the rapid movement of both vessels in the rough waters and the difficulty in achieving sufficiently satisfactory alignment between boat 14 and barge 10 to allow coupling unit 16, 16' to be extended to interconnect with vertical channels 18, 18'.
Another drawback of the prior art just described is that once the boat 14 is connected with barge 10, the draft of barge 10--the amount, or depth, of barge 10 which is below water--cannot change appreciably. For example, if boat 14 connects with barge 10 while barge 10 is loaded and sitting low in the water (a deep draft), boat 14 will connect near the upper portion of vertical channels 18, 18'. If the barge is then unloaded without disconnecting boat 14, the barge will rise in the water and begin to lift the bow of boat 14 out of the water as the draft of barge 10 becomes more shallow. Conversely, if boat 14 connects with barge 10 while barge 10 is empty and barge 10 is then subsequently filled, the draft of barge 10 will increase and barge 10 will sink further down into the water. This could ultimately result in forcing boat 14 down into the water, and could result in sinking boat 14.
In many types of articulated boat and barge applications, the loading and unloading of barge 10 is not an issue. In these cases, boat 14 approaches and connects with barge 10 when it is already loaded. Boat 14 then pushes barge 10 to the desired location where boat 14 disconnects from barge 10 before it is unloaded. In these types of applications, the respective drafts of boat 14 and barge 10 do not change. However, there are types of applications in which it is desirable to connect boat 14 to an empty barge 10, then move the barge to a point where it can be loaded with a commodity, followed by moving the loaded barge to a different location where the commodity can be unloaded. If this sequence of events were to occur on a river or other relatively calm or protected waterway, it would not be difficult for boat 14 to disconnect from barge 10, wait for the barge to be loaded or unloaded, and the draft of barge 10 to change and stabilize, and then to reconnect boat 14 to barge 10. However, if this connection and reconnection between boat 14 and barge 10 is to take place on the open sea or in rough seas, this sequence of events cannot be effected as boat 14 and barge 10 are, generally, incapable of successfully uncoupling and recoupling in seas presenting even slight swells.
Therefore, a substantial need exists for a device and method of interconnecting a tug or pusher boat to a barge which permits the draft of the barge to change while allowing the connection between the pusher boat and the barge to compensate for the vertical movement of barge while avoiding any connecting and reconnecting of the boat and barge.